1. Field of the Invention
This invention relates to an instrument for facilitating the introduction of transvenous leads into a human body, and more particular relates to valves for use in such an instrument.
2. Description of the Related Art
The use of electrically conducive transvenous lead, particularly cardiac pacing leads, is well known in the medical field. Many different methods and tools have been proposed in the prior art for allowing such leads to be introduced into the patient's subclavian vein via a relatively small incision. Often, medical device manufacturers may provide an introducer set to be used by doctors in implanting pacing leads.
A common feature of any method for introducing a lead into a patient's blood vessel is that a hollow, tubular instrument is required to provide a temporary passage or conduit into the blood vessel, though which the lead may be slid to enter the blood vessel. Such a conduit also allows blood to escape from the blood vessel, and may allow air to enter the blood stream, possibly leading to embolic complications.
In addition to the potential adverse clinical effects of leakage of blood and air through an introducer sheath, the flow of blood out of an introducer sheath is likely to make the physician's task more difficult, and may encourage the physician to perform the introduction procedure more hastily. This, in turn, can increase the tension associated with the introduction procedure, and the risk that mistakes will be made.
In the prior art, it is commonly suggested that the physician can prevent (or at least restrict) the flow of blood out of an introducer sleeve while the pacing lead is being prepared for introduction into the vein by placing his or her thumb over the exposed end of the introducer sleeve. A similar "solution" to the leakage problem that is sometimes practiced in the art is to squeeze or pinch the exposed end of the introducer sleeve between the thumb and forefinger.
Neither of these methods for reducing the undesired flow of fluids and air through the introducer sleeve is deemed by the inventor to be acceptable. In both cases, at least one of the physician's hands is required, thereby making it difficult for the physician to attend to other or more important matters. Moreover, squeezing the exposed end of the introducer sheath can deform or even break the introducer at that point, making lead insertion difficult and increasing the danger of damage to the lead as it passes through the introducer.
In addition, neither placing the thumb over the end of the introducer, nor squeezing the end of the introducer, will be sufficiently effective in preventing the flow of blood and air in the introducer once a guide wire has been threaded through the introducer. Also, the configuration of the end of some types of introducer sheath is such that it is difficult or impossible to seal the end of the introducer shut with the thumb.
A tricuspid valve system for catheter (as opposed to lead) introducers is also deemed to be unacceptable for use in conjunction with lead introducers. The tricuspid valve arrangement for catheters could damage the sensitive lead tip of a placing lead. The application of pressure required to open the tricuspid valve can result in distortion or breakage of the lead tip. Moreover, some presently known tricuspid systems are lubricated with silicone-based oil. The electrical properties of pacing/sensing leads, and the chemical properties of steroid-eluting lead tips and the like, can be severely affected by coming in contact with the oil.
A valve for reducing undesired flow of fluids and air through an introducer sleeve is described in U.S. Pat. No. 5,441,504 (Pohndorf et al., issued Aug. 15, 1995) and assigned to Medtronic, Inc. Although the valve described in that patent is a substantial advance in the art, it nonetheless can prove troublesome during the dilation procedure for certain practitioners who may require the use of two hands in order to properly manipulate the valve and hold the introducer assembly at the same time. The present invention is directed to a solution for this problem and enables an introducer assembly and valve to be operated with a single hand while a lead is being inserted into a patient.